<!DOCTYPE html>
<html lang="zh">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<style>
  #div1 {
    width: 200px;
    height: 100px;
    background: #CCC;
    border: 1px solid #999;
    display: none;
  }
</style>

<body>

  <input type="checkbox" onmouseover="document.getElementById('div1').style.display='block'"
    onmouseout="document.getElementById('div1').style.display='none'" />

  <div id="div1">
    提示内容
  </div>

</body>

</html>